1. Field
Example embodiments relate to a copolymer, a composition for forming banks, and a method for forming banks using the composition. Other example embodiments relate to a copolymer of a perfluoropolyether derivative and a photosensitive polymer, a composition for forming banks comprising the copolymer, and a method for forming banks using the composition.
2. Description of Related Art
In recent years, polymeric materials have attracted increased attention as electrical and electronic materials in a wide variety of applications, e.g., functional electronic devices and optical devices, because of their ease of molding into fibers and films, improved flexibility, increased conductivity and decreased production costs. Among devices using such electrically conductive polymers, organic thin film transistors may be fabricated by relatively simple techniques, e.g., printing, at decreased costs. In addition, organic thin film transistors may be advantageous in that they may be easier to process and may be highly compatible with flexible substrates. Based on these advantages, a number of studies on organic thin film transistors are being undertaken.
On the other hand, solution processing techniques, for example, printing techniques, are currently being researched due to improved processability and increased economic efficiency in the fabrication of organic electronic devices, e.g., display devices (e.g., electroluminescence devices and light-emitting diode devices). However, when a liquid material (an ink material) is filled and a thin film pattern is formed to fabricate an organic electronic device by a solution processing technique, there may arise problems that the liquid material overflows and is introduced into pixel regions of adjacent organic electronic devices, resulting in degradation of the characteristics of the adjacent organic electronic devices. To overcome these problems, banks may be formed as partition members that divide pixel regions to prevent or reduce occurrence of cross-talk between devices and to define desired regions so that an ink material may be filled only within the desired regions.
For example, when a photoresist using an organic solvent is used to form banks in the fabrication of a bottom contact type or top gate type organic thin film transistor, overflow of the organic solvent may lead to degradation of an organic insulating film, resulting in deterioration of the performance of the organic thin film transistor.
To solve these problems, many methods have been attempted. For example, one example of such a method may form banks by spin coating polyimide to form a thin film, coating a photoresist on the thin film, baking the resulting structure, followed by UV irradiation and development by photolithography to etch the polyimide. This method may additionally involve surface treatment of the banks to increase the contact angle. Other works have suggested a method for forming banks which may include spin coating a polymeric compound to form a thin film, stamping the thin film, followed by baking. This method may additionally involve surface treating the banks with plasma.
However, the disadvantage of these methods may be that when organic electronic devices are fabricated using bottom gate type insulating films, which may be general structures of display arrays, they may be exposed to organic solvents, e.g., solvents of bank materials, photoresist solvents, developing solvents and/or photoresist strippers, causing degradation in the characteristics of the devices. Because organic solvents of ink materials used to fabricate organic electronic devices have a decreased surface contact angle, the ink materials to be filled between banks may exhibit decreased definition for the banks, resulting in deteriorated performance of the devices.